1. Field of the Invention
The present invention relates to a compressed-air vibrator with a cylindrical housing confined between closure covers, within which there is arranged a piston reciprocated by the compressed air, whereby the compressed air is alternatingly introduced into the two working chambers through a central inlet groove in the cylinder bore and through axial bores which discharge through the end surfaces of the piston, and wherein the air is conveyed out of the chambers through outlets which are controlled by the piston edges.
2. Discussion of the Prior Art
Compressed-air vibrators of this type have become known in the form of various embodiments. Mostly they evidence a complicated construction and, in addition, neccessitate an expensive pressurized oil lubrication which is undesirable for various purposes of application. From German Published Patent Application No. 23 41 219 there has also become known a compressed-air vibrator which operates without an auxiliary pressurized oil lubrication. The cylinder is assembled from inner and outer sleeves which are threaded together, wherein annular grooves are provided intermediate the inner and outer sleeves for the outflowing compressed air, and which serve for cooling. The construction of these apparatuses is extremely complicated and their manufacture requires large demands and is expensive.
The compressed-air vibrators of the above-mentioned type further have the property that, in the horizontal position, the piston will hunt precisely in the center of the hollow cylinder when the compressed air infeed is shut off. When compressed air is again conveyed into the apparatus in this neutral piston position it is not possible to effect a restart due to the closed off inlet bore. The previously known piston-type vibrators accordingly, are equipped with (a) built-in springs which press the piston towards one side, or (b) with an auxiliary valve control, or (c) with fine starting grooves on the piston, which measures facilitate restarting even in the horizontal position of the apparatus. The negative aspects of these three methods are: (a) fracture of the spring and therewith connected possible destruction of the apparatus, (b) the valve control is expensive in construction and in its assembly at the working site, (c) the possibility of the plugging up of the starting grooves through dirt particles contained in the compresed air, the leakage losses during operation.